The present invention relates to an improved electrode for a moisture meter of the type which determines the water content of a powdery or granular material by measuring its electrostatic capacity.
Various methods have been proposed and used for the measurement of moisture which is contained in powdery or granular material. Among the methods used, there is a method which measures the electrostatic capacity of the sample in order to determine the water content. In this method, measuring electrodes, which are connected in parallel with a resonance circuit, are inserted into a sample for measuring the electrostatic capacity between the electrodes as the change in electrostatic capacity in the resonance circuit. Since the electrostatic capacity of the sample is proportional to the water content, the latter can be determined by measuring the former.
For a moisture meter of this type, an electrode has normally been used which includes a high-voltage electrode, a plurality of ground electrodes which are arranged in parallel with the high-voltage electrode, and an insulator to which said electrodes are secured.
The conventional electrode described includes a few drawbacks. First, if the electrode is inserted into the sample, not all the way to the root of the electrodes, but incompletely (because the surface of the sample is not level or for any other reason) the measurement which would result would be lower than the true value.
Second, in the case where drift compensation is performed after actual moisture measurement, if some of the sample remains on the base portion of the electrode, the drift compensation would be inaccurate because of the effect of the remaining sample which accordingly increases the electrostatic capacitance between the electrodes.
Thirdly, the effect of stray capacitance on the measuring results is not negligible.